Project Summary/Abstract This K23 award provides the PI with mentored research career development training necessary to become an independent researcher capable of developing and testing innovative interventions targeting problematic use of addictive substances and other maladaptive patterns of behavior associated obesity or other comorbid medical and psychiatric conditions. Overweight and obese smokers are disproportionately at risk for disease, disability, and premature death but may be reluctant to give up smoking due to the fear of subsequent weight gain and trouble managing their weight without cigarettes. Applying weight gain prevention as part of a multiple health behavior change (MHBC) program prior to smoking cessation, can help overweight and obese individuals lose weight and buffer against post-cessation weight gain. Achieving some degree of success with behavioral weight loss may result in decreased negative affect, increased future- oriented decision-making, and increased self-efficacy to manage weight and change smoking with great potential impact on subsequent smoking cessation outcomes. The current proposal will develop this MHBC intervention for treatment- seeking overweight and obese smokers and qualitative focus group data and data from an open series of patients to refine treatment. Next, a small 2-group randomized controlled clinical trial will be conducted with 60 overweight or obese smokers (BMI ? 25) assigned to either weight gain prevention (an intervention based on self-regulation approaches to produce and maintain weight loss as a way to effectively prevent weight gain) or healthy lifestyle education (an attention- placebo comparison condition matched for contact time) before smoking cessation treatment. Participants will receive 8 weeks of weight gain prevention or lifestyle education followed by 8 weeks of cognitive behavioral therapy for smoking cessation with combination nicotine replacement therapy. Smoking cessation counseling sessions will include brief maintenance information according to assigned condition. Intervention feasibility and acceptability will be assessed and preliminary data regarding efficacy of the intervention on weight and smoking outcomes will be assessed. The PI will work with an experienced and knowledgeable team of mentors (Drs. Damaris Rohsenow, Rena Wing, Rosemarie Martin, and Jennifer Tidey) to develop areas of training relevant to this proposal including: (1) conducting randomized controlled trials for health behavior change interventions for smokers with comorbid conditions, with an initial primary focus on obesity, (2) implementing the stage model of treatment development for clinical behavioral therapy research including qualitative methodology for therapy development, (3) learning advanced statistical techniques for analyzing longitudinal data in clinical trials, and (4) strengthening professional research career development skills. Preliminary efficacy data obtained in the proposed study represents an important first step in creating an innovative, empirically-supported, MHBC intervention targeting smoking and obesity with high significance to public health.